This invention relates to prosthetic feet and, more particularly, to multi-piece prosthetic foot assemblies having improved functional properties.
The basic requirements of an acceptable prosthetic foot are that it will provide a stable support for the amputee throughout a reasonable range of activities and permit the amputee to walk with a normal stride. To achieve this normal stride, the prosthetic foot must flex during walking as the foot continually moves through the heel-strike, foot-flat, and toe-off cycle. It must also, throughout this cycle, provide transverse stability particularly at toe-off, when the entire weight of the amputee is applied to the forward portion of the prosthetic foot. Prior art prosthetic feet typically are substantially transversely inflexible which interferes with side to side balancing when walking on uneven surfaces. Unlike the natural foot, these types of prosthetic foot assemblies do not sense nor correct themselves with this unevenness and an unanticipated sideways tilting of the foot at toe-off results in an imbalance at a critical portion of the stride.
Amputees are no longer satisfied to sit in a wheelchair or to be content with a stilted, unnatural walking motion. An amputee often strives to duplicate physical activities which were conducted before the amputation. These activities may include rigorous physical activities such as running, playing basketball, and dancing.
In order to be commercially acceptable, prosthetic feet must duplicate the motions of the natural foot as much as possible. These motions include side to side stability at the toe section of the foot where weight can be exerted on each side of the foot. The ankle joint must have torsional flexibility transverse to the up and down motion of the ankle which pivotally lowers and raises the foot.
The added torsional motion of the joint in the artificial foot adds a degree of stress on the resilient pads located between the members of the artificial foot which are not otherwise present in a foot that has limited motion in only the up and down direction relative to pivotable raising and lowering of the foot.
Modern, high-tech, prosthetic feet strive to more accurately replicate the function the natural foot. In order to achieve this end, the designs of these artificial feet include more and more moving parts which impacts on the reliability and aesthetic properties of the prosthetic foot assemblies. Because of the unusually high loads imposed on the joints of prosthetic foot, compressive elements such as bumpers and cushions are subject to fatigue and are prone to failure. Accordingly, it would be desirable to have a bumper or cushion design which increase the reliability of a prosthetic foot assembly while decreasing the frequency of maintenance required to maintain the prosthetic foot assembly. Additionally, it would be desirable to have bumpers or cushions which not only have extended life, but have improved dynamic characteristics (user satisfaction).
Again, related to the aesthetics of prosthetic feet, amputees do not wish to call attention to themselves by making noise as they walk. Complex prosthetic foot designs, over thousands of load cycles, can commonly cause noises as the amputee walks with the prosthetic foot assembly. Even those amputees who do not wear cosmetic covers and feel comfortable with the xe2x80x9chigh-techxe2x80x9d look of their artificial limb components do not appreciate the noise generated by their prosthetic devices which can be a mental distraction. Accordingly, it would be desirable to have a prosthetic foot assembly in which noise can be eliminated to make the prosthetic foot assembly which is both aesthetically and functionally more pleasing to the wearer.
In attempts to make prosthetic foot assemblies which function more like a natural foot, very complex, multi-axis assemblies have been designed. However, these designs are costly and, therefore, can exclude segments of amputees from obtaining these more functional prosthetic devices. Accordingly, it would be desirable to have a more economical prosthetic foot assembly which provides many of the benefits of multi-axis prosthetic foot assemblies while having only one pivotal axis.
In accordance with one aspect of the present invention, a prosthetic foot assembly includes an ankle member pivotally connected to a heel member which is in turn pivotally connected to an elongate metatarsal-toe member about two substantially parallel axles. A compressible element having first and second substantially circular bearing surfaces is engaged between a portion of the heel member and a portion of the metatarsal-toe member to resist upward pivotal movement of a forward end of the metatarsal-toe member relative to the heel member. The compressible element has a median portion of the compressible element or bumper spaced apart from one of the bearing surfaces has a smaller diameter than the diameter of at least one of the first and second bearing surfaces.
In accordance with another aspect of the present invention, the bearing surfaces of the compressible elements engaging an engagement surface of either the ankle member and/or the heel member include at least one interrupted bearing surface in order to prevent the generation of noise from the foot assembly.
Additionally, in accordance with the present invention, the engagement surfaces of the ankle member and/or heel member can also be interrupted in order to abate noises generated between moving surfaces of the foot assembly.
In accordance with another aspect of the present invention, an adaptor assembly for attaching a prosthetic foot assembly having an ankle member, a heel member, and a metatarsal-toe member to either an endoskeleton or an exoskeleton includes an adaptor member having a top surface adapted to engage an endoskeleton or an exoskeleton and a bottom surface adapted to engage the ankle member. The adaptor member includes a primary fastener for fixation of the adaptor member to the ankle member and also includes a secondary fastener which decreases the magnitude of stress distributed to the primary fastener by preventing the back of the adaptor element from lifting away from the ankle member under loading conditions.
According to another aspect of the present invention, a prosthetic foot assembly has an ankle member which is in turn pivotally connected to a combination for feet/heel member (xe2x80x9ca foreheelxe2x80x9d member) about a single axle. The ankle member has two shoulder portions with apertures therethrough that are aligned with the central bore through the foreheel member to form a passage for the axle. The foreheel member includes a central portion having a central transverse bore having a limiter eccentrically disposed therein. The axle passes through two spaced resilient bushings that are positioned in the counter-bores. Interposed between the two resilient bushings is a semi-rigid liner with an inner diameter size to receive the axle. The resilient bushings allow for transverse pivotal motion about the axis of the axle while the semi-rigid liner de-couples the resilient bushings from the axle allowing the axle and semi-rigid bushing to slide relative to each other.
Other objects, features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in conjunction with the accompanying drawings.